add a Buy Botc shares button

The goal is to make pretty easier for a member to buy new botc shares.

The Buy botc shares button should create a wallet to wallet event to the Botc admin account: which have this token: 5937fc10a4c67

and at same time an update of new shares bought in the members.bankofthecommons.coop account. if the second integration is more difficult, a middle step could be just to update to support@bankofthecommons.coop for the update in ocp, being done manually.